U.S. patent number 8,748,528 [Application Number 13/512,500] was granted by the patent office on 2014-06-10 for vapor permeable barrier coating applicable at low temperature.
This patent grant is currently assigned to W. R. Grace & Co.-Conn.. The grantee listed for this patent is Antonio J. Aldykiewicz, Jr., Neal S. Berke, Xia Cao, Jyoti Seth, Robert A. Wiercinski. Invention is credited to Antonio J. Aldykiewicz, Jr., Neal S. Berke, Xia Cao, Jyoti Seth, Robert A. Wiercinski.
United States Patent |
8,748,528 |
Cao , et al. |
June 10, 2014 |
Vapor permeable barrier coating applicable at low temperature
Abstract
Disclosed is a coating composition that includes an aqueous
emulsion of a hydrophobic acrylic polymer, a water-soluble polymer,
and an inorganic filler, and further includes a freezing-point
lowering component to permit low temperature application. The
freezing-point lowering component will preferably include a
water-soluble, corrosion inhibiting salt. The coating composition
will also optionally and preferably include an evaporation
enhancing component to promote faster drying and skin formation at
low temperatures. The coating composition may be coated onto a
construction surface (e.g., by spraying) where, after drying, it
will form a fully adhered barrier membrane that is water-vapor
permeable, but air and liquid-water impermeable. Such membrane will
preferably have sufficient coating thickness and sufficiently high
elongation that it will bridge joints and cracks.
Inventors: |
Cao; Xia (Acton, MA),
Wiercinski; Robert A. (Lincoln, MA), Berke; Neal S.
(Chelmsford, MA), Aldykiewicz, Jr.; Antonio J. (Lexington,
MA), Seth; Jyoti (Andover, MA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Cao; Xia
Wiercinski; Robert A.
Berke; Neal S.
Aldykiewicz, Jr.; Antonio J.
Seth; Jyoti |
Acton
Lincoln
Chelmsford
Lexington
Andover |
MA
MA
MA
MA
MA |
US
US
US
US
US |
|
|
Assignee: |
W. R. Grace & Co.-Conn.
(Columbia, MD)
|
Family
ID: |
43618338 |
Appl.
No.: |
13/512,500 |
Filed: |
November 18, 2010 |
PCT
Filed: |
November 18, 2010 |
PCT No.: |
PCT/US2010/057148 |
371(c)(1),(2),(4) Date: |
May 29, 2012 |
PCT
Pub. No.: |
WO2011/066160 |
PCT
Pub. Date: |
June 03, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120231170 A1 |
Sep 13, 2012 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
61265159 |
Nov 30, 2009 |
|
|
|
|
Current U.S.
Class: |
524/503 |
Current CPC
Class: |
C09D
133/08 (20130101); C09D 133/08 (20130101); C08L
2666/04 (20130101); C08L 29/06 (20130101); C08K
3/28 (20130101) |
Current International
Class: |
C08L
29/04 (20060101) |
Field of
Search: |
;524/503 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2006076186 |
|
Jul 2006 |
|
WO |
|
WO 2006076186 |
|
Jul 2006 |
|
WO |
|
Other References
Henry Company, Technical Data Sheet "AIR.sub.--BLOC 07", dated Jun.
23, 2006, 3 pages. cited by applicant .
Henry Company, Technical Data Sheet "AIR.sub.--BLOC 31", dated Jul.
15, 2002, 3 pages. cited by applicant .
Helmut, Form PCT/ISA/210, International Search Report for
PCT/US2010/057148, dated Nov. 3, 2011, 4 pages. cited by applicant
.
Helmut, Form PCT/ISA/237, Written Opinion of the International
Searching Authority for PCT/US2010/057148, dated Nov. 3, 2011, 4
pages. cited by applicant.
|
Primary Examiner: Choi; Ling
Assistant Examiner: Reuther; Lanee
Attorney, Agent or Firm: Leon; Craig K.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a 371 of PCT/US2010/057148, filed on Nov. 18,
2010, which claims the benefit of U.S. Provisional Application No.
61/265,159 filed on Nov. 30, 2009.
Claims
The invention claimed is:
1. A liquid coating composition useful for providing a water-vapor
permeable, air barrier membrane by coating on a construction
surface, the liquid coating composition being an aqueous emulsion,
comprising: a hydrophobic acrylic polymer, wherein the hydrophobic
acrylic polymer comprises about 50% to 97% by weight based on total
solids in the liquid composition, the hydrophobic acrylic polymer
comprising a homopolymer or a copolymer of an acrylic ester having
a repeating group represented by the structure
--(--CH.sub.2--C(R.sup.1)HCOOR--)-- wherein R is a C2-C8 alkyl
group and R.sup.1 is H or CH.sub.3; a water soluble polymer,
wherein the water-soluble polymer comprises about 1% to 20% by
weight based on total solids in the liquid composition, and wherein
the water-soluble polymer comprises polyvinyl alcohol, polyethylene
oxide, water soluble cellulosic polymers, hydrolyzed maleic
anhydride polymers and copolymers, polyvinylpyrrolidone, sulfonated
polystyrene, polysulfoethyl acrylate, poly(2-hydroxyethylacrylate),
polyacrylamide, poly(acrylic acid) and alkali metal salts thereof,
natural or synthetically modified polysaccharides, proteins,
alginates, xanthan gums, or guar gums, or combinations of two or
more of such water soluble polymers; an inorganic filler, wherein
the inorganic filler comprises about 2-40% by weight based on total
solids in the liquid composition; a freezing-point lowering
component comprising a water-soluble metal salt, wherein the
water-soluble metal salt comprises about 0.5-15% by weight of the
total weight of the liquid composition, said water-soluble metal
salt comprising calcium nitrite, sodium nitrite, or a mixture
thereof; and an evaporation enhancing agent in an amount of about
0.5-15% by weight of the total weight of the liquid composition,
the evaporation enhancing agent comprising at least one solvent
selected from methanol, ethanol, oxybis-propanol, vinyl acetate,
butyl acetate, ethyl acetate, methyl isobutyl ketone, methyl ethyl
ketone, or a combination of two or more of these solvents; and
wherein the liquid composition comprises water in an amount of
about 30-50% by weight of the total weight of the liquid
composition.
2. The composition of claim 1 wherein the water-soluble metal salt
further comprises a water-soluble, alkali, alkaline earth or rare
earth metal chloride salt nitrate, or a combination of two or more
of these salts.
3. The composition of claim 1 wherein the water-soluble metal salt
further comprises sodium chloride, potassium chloride, calcium
chloride, magnesium chloride, calcium nitrate, cerium chloride,
cerium nitrate, calcium magnesium acetate, potassium formate, or
sodium silicate, or a combination of two or more of these
salts.
4. The composition of claim 1 wherein the evaporation enhancing
agent comprises ethanol.
5. The composition of claim 1 wherein the evaporation enhancing
agent comprises a volatile organic solvent.
6. The composition of claim 1 wherein the evaporation enhancing
agent comprises a volatile organic solvent that forms an azeotrope
with water.
7. The composition of claim 1 wherein the hydrophobic acrylic
polymer comprises a copolymer of butyl acrylate and styrene.
8. The composition of claim 7 wherein the water soluble polymer
comprises polyvinyl alcohol.
9. A liquid coating composition useful for providing a water-vapor
permeable, air barrier membrane by coating on a construction
surface, the liquid coating composition being an aqueous emulsion,
comprising: a hydrophobic acrylic polymer, wherein the hydrophobic
acrylic polymer comprises about 50% to 97% by weight based on total
solids in the liquid composition; a water soluble polymer, wherein
the water-soluble polymer comprises about 1% to 20% by weight based
on total solids in the liquid composition, and wherein the
water-soluble polymer comprises polyvinyl alcohol, polyethylene
oxide, water soluble cellulosic polymers, hydrolyzed maleic
anhydride polymers and copolymers, polyvinylpyrrolidone, sulfonated
polystyrene, polysulfoethyl acrylate, poly(2-hydroxyethylacrylate),
polyacrylamide, poly(acrylic acid) and alkali metal salts thereof,
natural or synthetically modified polysaccharides, proteins,
alginates, xanthan gums, or guar gums, or combinations of two or
more of such water soluble polymers; an inorganic filler, wherein
the inorganic filler comprises about 2-40% by weight based on total
solids in the liquid composition; a freezing-point lowering
component comprising a water-soluble metal salt, wherein the
water-soluble metal salt comprises about 0.5-15% by weight of the
total weight of the liquid composition, said water-soluble metal
salt comprising calcium nitrite, sodium nitrite, or a mixture
thereof; and an evaporation enhancing agent in an amount of about
0.5-15% by weight of the total weight of the liquid composition,
the evaporation enhancing agent comprising at least one solvent
selected from methanol, ethanol, oxybis-propanol, vinyl acetate,
butyl acetate, ethyl acetate, methyl isobutyl ketone, methyl ethyl
ketone, or a combination of two or more of these solvents; and
wherein the liquid composition comprises water in an amount of
about 30-50% by weight of the total weight of the liquid
composition.
10. The composition of claim 9 wherein the evaporation enhancing
agent comprises ethanol.
11. The composition of claim 9 wherein the hydrophobic acrylic
polymer comprises a homopolymer or a copolymer of an acrylic ester
having a repeating group represented by the structure
--(--CH.sub.2--C(R.sup.1)HCOOR--)-- wherein R is a C2-C8 alkyl
group and R1 is H or CH.sub.3.
12. The composition of claim 9 wherein the evaporation enhancing
agent comprises a volatile organic solvent that forms an azeotrope
with water.
Description
FIELD OF THE INVENTION
The present invention relates to an aqueous, liquid-applied coating
composition that can be applied at low temperature and that dries
to produce a water impermeable, water-vapor permeable, air barrier
coating. The coating composition includes an emulsion of a
hydrophobic acrylic polymer phase and a continuous water-soluble
polymer phase, and further includes a freezing-point lowering
component to permit low temperature application.
BACKGROUND OF THE INVENTION
Water-vapor permeable, air barrier coatings can be formed by
applying a liquid coating composition onto a building construction
surface. The liquid coating may be spray-applied, brushed, troweled
or otherwise coated onto the target substrate, which may include a
cementitious surface, such as cement, mortar, masonry, concrete,
shotcrete, gypsum, gypsum board and gypsum sheathing, or some other
building construction surface, such as wood, plywood, oriented
strand board, fiberboard, particle board, rigid insulation,
etc.
One product currently available from Henry Company, California, is
sold under the trade name AIR-BLOC 07. This liquid product can be
troweled or spray applied, then cures to form a coating that
resists air leaking while remaining permeable to the passage of
water vapor at 7 perms (or 400 ng/Pa.m.sup.2.s) per ASTM E96 (Henry
Technical Data sheet dated 06/23/06). The composition is a
one-component solvent-based, SBR-modified bitumen and includes 1-5
parts Bentonite, 7-13 parts calcium carbonate, 10-30 parts of
cellulose fiber, 1-5 parts of ethylene glycol, 10-30 parts of
Stoddard solvent (C.sub.7-C.sub.12 hydrocarbon mixture) and other
minor ingredients (Air-Bloc 07 MSDS issued at Nov. 10, 2008). The
coating formed by this product is believed to have a hydrophilic
domain or channel formed by cellulose fiber and Bentonite allowing
passage of water-vapor through the coating. Although this
solvent-based product can be applied as low as 10.degree. F., the
coating shows low elongation and poor crack bridging properties.
Because this product is solvent-based, it has higher VOC (i.e.
close to 250 g/L), thus raising environmental concerns and
requiring special solvents to clean equipment after use. In
addition, solvent-based products are incompatible with damp
surfaces and require a fully dry surface prior to applying the
product, which can be a challenge in a low temperature
environment.
Another product available from Henry Company is sold under the
trade name AIR-BLOC 31. This water-based composition can be
spray-applied and cures to form a membrane that blocks air and air
leakage and purportedly achieves a water vapor permeance of 12.3
perms (or 704 ng/Pa.m.sup.2.s) under ASTM E-96 (Henry Technical
Data Sheet dated Jul. 15, 2002). This product comprises about 65%
total solids, wherein the solids comprise approximately 15 parts
calcium carbonate (a typical filler), 35 parts wax (polyethylene or
hydrocarbon wax; considered here to act as a filler because it does
not form a film), and 50 parts vinyl acetate-acrylate copolymer. It
is believed that this product has a microporous structure as a
result of high filler level that exceeds the critical pigment
volume concentration.
Another type of liquid coating composition for protecting exterior
wall and roof surfaces is disclosed in U.S. Pat. No. 4,859,723.
This water-based composition includes a water-dispersible polymeric
binder (e.g., acrylic polymer) and pigment and filler material,
including clay, such that the composition has a pigment volume
concentration (PVC) greater than 15. These coating compositions are
said to be suitable for application to bituminous built-up roofs,
including hot mopped asphalt, and compositions with very low water
permeability are considered especially useful. These compositions
may include auxiliary agents such as preservatives, buffers,
coloring agents, plasticizers, fire retardants, coalescents,
disinfectants, and stabilizers (e.g., an anti-freeze material).
However, the patentee suggests that the compositions should be
applied at ambient temperatures of 50-100.degree. F. (10-38.degree.
C.).
An improved water-based, liquid-applied vapor permeable membrane
composition is disclosed in WO 2006/076186 and is sold under the
tradename PERM-A-BARRIER.RTM. VP (W.R. Grace & Co.-Conn.). This
membrane composition includes a water soluble polymer (e.g. PVOH),
a hydrophobic acrylic polymer and a filler (and other minor
components) to provide a water-vapor permeable air barrier membrane
on a construction surface. The membrane has good flexibility and
crack-bridging characteristics. As a water-based system, it is
environmentally friendly and compatible with damp surfaces.
However, it can not be used below freezing temperatures.
It is generally difficult to apply a liquid coating at low
temperatures because the viscosity of the material increases as
ambient temperatures decrease and the curing rate of the membrane
slows down, potentially reducing the quality of the membrane
produced. In addition, a water-based product cannot be applied
below freezing temperatures because it will freeze. Freezing will
also cause deterioration of coating properties.
It would be advantageous to provide a water-based, liquid-applied
vapor permeable membrane composition that may be applied at low
temperatures, particularly at temperatures below freezing (e.g.,
temperatures in the range of -10.degree. C. to 0.degree. C.), and
that will dry to form a membrane film at such low temperatures.
SUMMARY OF THE INVENTION
The present invention is directed to a liquid coating composition
that includes an aqueous emulsion of a hydrophobic acrylic polymer,
a water-soluble polymer, and an inorganic filler, and further
includes a freezing-point lowering component to permit low
temperature application. The freezing-point lowering component will
preferably include a water-soluble, corrosion inhibiting salt,
particularly an inorganic salt. The coating composition will also
optionally and preferably include an evaporation enhancing
component to promote faster drying and skin formation at low
temperatures. The coating composition may be coated onto a
construction surface (e.g., by spraying) where, after drying, it
will form a fully adhered barrier membrane that is water-vapor
permeable, but air and liquid-water impermeable. Such membrane will
preferably have sufficient coating thickness and sufficiently high
elongation that it will bridge joints and cracks.
An exemplary membrane of the invention, formed by spraying the
liquid coating composition onto a substrate surface, will
preferably have an average dry thickness of 0.25-2.0 mm (10-80
mils), and will have a water vapor permeability of 1-50 perms, more
preferably 5-35 perms (ASTM E-96). At such thicknesses, membranes
made from the coating compositions of the invention exhibit high
elongation (preferably about 200% to about 1000%), which bestows
excellent crack-bridging capabilities.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graphic illustration of the degree of drying of certain
compositions of the present invention.
FIG. 2 is a graphic illustration of the degree of drying of certain
compositions of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment, the present invention is directed to a liquid
coating composition, useful for providing a water-vapor permeable,
air barrier membrane on a construction surface. The liquid coating
composition is an aqueous emulsion comprising a hydrophobic acrylic
polymer, a water soluble polymer, an inorganic filler, and a
freezing-point lowering component. The coating composition will
also optionally and preferably include an evaporation enhancing
component. Typically the liquid coating composition will comprise
water in an amount of 30% to 50% by total weight of the liquid
composition.
The hydrophobic acrylic polymer may be a homopolymer or a copolymer
of an acrylic ester and will have a repeating group represented by
the structure --(--CH.sub.2--C(R.sup.1)HCOOR--)-- wherein R is a
C.sub.2-C.sub.8 alkyl group and R.sup.1 is H or CH.sub.3.
Preferably, R represents an ethyl, propyl, butyl, octyl or ethyl
hexyl group, and R.sup.1 is H. More preferably, the hydrophobic
acrylic polymer is a butyl acrylate polymer. The acrylic polymer
may also comprise other monomers as well including, but not limited
to, styrene, vinyl acetate, and vinyl chloride. A preferred acrylic
polymer is a copolymer of butyl acrylate and styrene wherein the
molar ratio of butyl acrylate/styrene is greater than 1, preferably
greater than 1.5. Typically, the acrylic polymer will have a glass
transition temperature of -55.degree. C. to 0.degree. C. The
hydrophobic acrylic polymer may be present in an amount of about
50% to 97%, preferably about 60% to 90%, by weight based on total
solids in the liquid composition.
The liquid coating composition additionally comprises a
water-soluble polymer. The water-soluble polymer should be present
in the liquid composition in an amount of 1% to 20%, preferably 3%
to 17%, by weight based on total solids in the liquid composition.
The level of water-soluble polymer is in addition to any
water-soluble polymer that may be used as a protective colloid in
the acrylic emulsion (if the emulsion is supplied by an emulsion
manufacturer). Preferably, the water-soluble polymer will have a
solution viscosity, at 4% by weight of the water-soluble polymer in
water, of about 2 to 50 centipoise (cps).
Suitable water soluble materials may include polyvinyl alcohol
(PVOH), polyethylene oxide (PEO), water soluble cellulosic polymers
(e.g., hydroxypropyl methyl cellulose, hydroxyethyl cellulose),
hydrolyzed maleic anhydride polymers and copolymers,
polyvinylpyrrolidone, sulfonated polystyrene, polysulfoethyl
acrylate, poly(2-hydroxyethylacrylate), polyacrylamide,
poly(acrylic acid) and alkali metal salts thereof, natural or
synthetically modified polysaccharides, proteins, alginates,
xanthan gums, and guar gums. Preferred water soluble polymers
include polyvinyl alcohol having a number average molecular weight
of 5,000 to 50,000, polyethylene oxide having an average molecular
weight of 5,000 to 200,000, and methyl ether or ethyl ether of
cellulose having a number average molecular weight of 3,000 to
20,000. The use of low MW versions of these polymers insures that
the liquid composition has a viscosity that is low enough to
facilitate spraying of the liquid composition, and the weight
fraction of water soluble polymer is high enough to insure high
water vapor permeability.
The liquid coating composition may further comprise an inorganic
filler in an amount of about 0-50%, preferably about 2-40%, and
more preferably about 3-30%, by weight based on total solids in the
liquid composition. Suitable inorganic filler materials include
calcium carbonate, talc, clay, silica, titanium dioxide,
wollastonite, mica, and vermiculite, and any other filler with a
high aspect ratio that improves physical properties or influences
barrier properties, and mixtures of two or more of these. The total
amount of all inorganic filler in the liquid composition typically
will provide a pigment volume concentration (PVC) of 1-25%,
preferably 3-18%. The PVC may be computed by multiplying the volume
of filler and other hard non-film forming ingredients by 100 and
dividing this by the total volume of solids. Preferably, the amount
of filler should be less than that required to exceed critical PVC
so that the membrane is not microporous. Preferably, the filler
material has an average particle size no less than 0.1 .mu.m and no
greater than 50 .mu.m.
The liquid coating composition additionally comprises a
freezing-point lowering component. This component will allow the
aqueous product to be stored, applied and dried at temperatures
below the freezing point of water. Conventional antifreeze
materials such as methanol, ethylene glycol, propylene glycol,
glycerol, and dimethyl sulfoxide (DMSO) are generally not suitable
for this application because too large a quantity is needed, which
may adversely affect the properties of the composition and, in some
cases, can slow down the drying time at low temperature. The
preferred freezing-point lowering component includes water-soluble
metal salts, particularly water-soluble inorganic salts, more
particularly water-soluble alkali and alkaline earth metal
salts.
Suitable metal salts include water-soluble, alkali and alkaline
earth (and rare earth) metal chlorides, nitrites and nitrates, for
example, sodium chloride, potassium chloride, calcium chloride,
magnesium chloride, calcium nitrite, calcium nitrate, sodium
nitrite, cerium chloride, cerium nitrate, as well as calcium
magnesium acetate (CMA), potassium formate, sodium silicate, etc.
or a combination of two or more of these salts. Such salts may also
be utilized in combination with conventional antifreeze materials.
The amount of metal salt(s) in the liquid composition will
generally comprise about 0.5-15%, preferably about 1-5% by weight
of the total liquid composition (or about 1-10% by weight of total
solids).
Preferred metal salts include alkali and alkaline earth metal
nitrites since such salts inhibit corrosion. The metal nitrites may
also provide some biocide activity and can be used at a relatively
low amount when combined with an evaporation enhancing component,
as described hereinafter. A most preferred metal salt is calcium
nitrite or a combination of calcium nitrite with an alkali metal
salt, such as sodium chloride. In the case where a combination of
calcium nitrite with an alkali metal salt is used, preferably the
ratio of calcium nitrite to alkali metal salt is about 1.5:1 to
about 2.5:1, more preferably about 2:1. Most preferably, the amount
of calcium nitrite, or calcium nitrite/alkali metal chloride, will
comprise about 0.5-2% by weight of the total liquid
composition.
A liquid coating composition applied on a building construction
surface may require good corrosion resistance since the coating may
come in contact with metal components in the building structure,
such as steel ties. Metal component are susceptible to corrosion
when exposed to moisture, and such corrosion can be exacerbated in
the presence of sulfates, chlorides and similar anions that may be
present in the water or in the coating that comes in contact with
the metal component. Thus, it may be advantageous to include a
corrosion inhibitor in the liquid coating composition. Nitrites are
excellent corrosion inhibitors for steel. From an environmental,
health and safety (EH&S) standpoint calcium salts are preferred
over potassium and sodium. Other suitable corrosion inhibitors are
molybdates (e.g. sodium molybdate), amines, sodium chromate,
potassium chromate, calcium chromates, strontium chromate, sodium
benzoate, zinc borate, or a combination of these inhibitors.
The liquid coating composition may optionally and advantageously
include an evaporation enhancing component to facilitate faster
drying of the coating composition to form a membrane film at low
temperatures, particularly below normal freezing temperatures. A
suitable evaporation enhancing component is a volatile organic
solvent. Suitable volatile organic solvents include methanol,
ethanol, xylene, diethylene glycol dibenzoate, styrenated phenol,
oxybis-propanol, dibenzoate propanol, vinyl acetate, butyl acetate,
ethyl acetate, methyl isobutyl ketone, methyl ethyl ketone, etc or
a combination of two or more of these solvents. Preferred organic
solvents are those that form an azeotrope with water. A most
preferred volatile organic solvent is ethanol. The amount of
volatile organic solvent in the liquid coating composition will
generally comprise about 0-20%, preferably about 0.5-15%, more
preferably about 0.5-5%, by weight of the total liquid composition.
Preferably, the VOC of the liquid composition will be less than 150
g/l, more preferably less than 50 g/l, most preferably less than 25
g/l.
The liquid coating composition may also include other optional
ingredients, as desired, including colorants or pigments (to impart
color to the membrane), rheology modifiers, antioxidants, LTV
stabilizers, antifoam agents, and biocides.
The liquid coating composition may be spray-coated, brushed,
troweled, or otherwise coated onto the target substrate, which is
typically a building construction surface. Substrates include
cementitious surfaces (e.g., cement, mortar, masonry, concrete,
shotcrete, gypsum) as well as gypsum board, and other porous
structures such as wood or plywood. Upon drying, the coating
composition will form an adherent membrane film on the
substrate.
Accordingly, the present invention provides a method for coating a
substrate surface, such as gypsum board, structures made of cement,
masonry, or concrete, or structures made of wood, comprising
applying the liquid coating composition to the substrate surface
(e.g., by spray coating) and allowing it to dry. The present
invention also pertains to composite structures formed by coating
such substrates surfaces with the afore-mentioned coating
compositions.
The present invention also provides a low temperature additive
composition comprising an aqueous solution of freezing-point
lowering component (as described above), and optionally containing
evaporation enhancing component (as described above). This additive
composition may be added to a conventional aqueous, liquid-applied
coating composition on site, prior to application of the coating
composition to a substrate surface, in order to render the coating
composition suitable for below freezing application. This
concentrated, aqueous additive composition will comprise, by
weight, about 5 to 30% of the freezing-point lowering component
(e.g. calcium nitrite) and about 10 to 60% of the evaporation
enhancing component (e.g., ethanol), if the latter is present. Of
course, other optional and desirable components (e.g., pH
adjusters, biocidal agents, defoamers, etc.) may be included as
desired.
Further advantages and features of the invention are described in
further detail in the examples that follow, which examples are
provided for illustrative purposes only. As will become evident,
the inclusion of calcium nitrite in the liquid coating composition
provides a lower freezing point (making application possible below
normal freezing temperatures), increased vapor permeability, and
reduced corrosion. The optional and preferred inclusion of ethanol
speeds drying time and reduces the amount of calcium nitrite needed
to lower the freezing point (i.e., ethanol and calcium nitrite act
synergistically to lower the freezing point). In addition, the
inclusion of an alkali metal salt, such as sodium chloride, in
combination with calcium nitrite, enables the use of lower amounts
of ethanol to enhance drying time at low temperatures while
providing the liquid coating composition with a lower, more
desirable, VOC and a higher flash point (i.e., lower
flammability).
Example 1
This example illustrates the effect of the freezing-point lowering
component (e.g., calcium nitrite and/or sodium chloride or CMA or
sodium silicate), optionally with evaporation enhancing component
(e.g., ethanol) and the ability of the liquid coating composition
to dry and form quality film on a construction surface (e.g.,
DensGlass and concrete masonry unit (CMU)). Various liquid coating
compositions are illustrated in Table 1. All the component amounts
are expressed in terms of weight percentage of the total liquid
mixture unless otherwise indicated. The acrylic polymer is BASF
ACRONAL S400 (solid content 57%). The PVOH is Celvol 203S
(Celanese). The "filler" identified in the Table includes the
inorganic filler (e.g., titanium dioxide) plus other minor
components such as pH adjusters, rheology modifiers, antioxidants,
UV stabilizers, antifoam agents, pigments and biocides.
The coating composition without low temperature additives (i.e.
formulation no. 1) could not be applied below the freezing point of
water because it solidified. Additionally, this composition
coagulated after it was brought back to a temperature above
0.degree. C. (32.degree. F.) (thawing) and was not able to form a
good quality membrane. Based on this observation, even if the
composition is able to be applied at a temperature just above
0.degree. C. (32.degree. F.), it may not be able to form quality
membrane if the temperature drops below 0.degree. C. (32.degree.
F.) before the composition dries. When the liquid coating
composition is modified by the addition of the conventional
antifreeze propylene glycol (formulation no. 2), this composition
does not freeze at -7.degree. C. (20.degree. F.). However, it would
not dry at the desired wet thickness of 2.2 mm (90 mil) to form a
solid membrane after 2-3 weeks at -7.degree. C. (20.degree. F.).
Thus, this formulation would not be suitable for outdoor
construction applications.
As can be seen from Table 1, the addition of salts like sodium
chloride, calcium nitrite, calcium magnesium acetate (CMA), sodium
silicate and combinations thereof can prevent freezing at
-7.degree. C. (20.degree. F.). The actual dosage varies depending
upon the type of additive(s). For example, calcium nitrite, when
used alone, may need to be present in an amount of about 4% (by
weight of total solution) to provide effective freezing-point
lowering properties, but a lower amount of total salts can be used
when combined with sodium chloride or ethanol. Compare no. 41 to
nos. 44, 32 and 34, for example. These compositions will also dry
in a reasonable time to form acceptable membranes, as further
described hereinafter.
TABLE-US-00001 TABLE 1 Formulations Composition Acrylic polyvinyl
Calcium Sodium Sodium Propylene Freeze at No latex alcohol Filler
Water nitrite chloride silicate CMA Ethanol Glycol- 20 F. 1 74.09
4.92 5.26 15.73 Yes 2 61.31 4.07 4.36 13.02 17.25 No 3 64.43 4.27
4.58 13.68 13.04 No 41 64.75 4.30 4.60 22.23 4.13 No 40 66.27 4.40
4.71 21.05 3.58 Yes 39 68.10 4.52 4.84 19.79 2.76 Yes 38 69.98 4.64
4.97 18.52 1.89 Yes 11 67.35 4.47 4.79 14.30 9.09 No 44 68.77 4.56
4.89 18.20 1.79 1.79 No 42 71.28 4.73 5.06 17.00 0.96 0.96 Yes 43
70.66 4.69 5.02 17.78 0.48 1.38 No 5 61.74 4.10 4.39 13.11 12.50
4.17 No 4 59.27 3.93 4.21 12.58 12.00 8.00 No 7 61.74 4.10 4.39
13.11 8.33 8.33 No 6 64.43 4.27 4.58 13.68 4.35 8.70 No 24 59.41
3.94 4.22 20.40 4.01 8.02 No 32 66.82 4.43 4.75 17.69 1.80 4.51 No
31 63.94 4.24 4.54 16.93 1.73 8.63 No 37 72.28 4.80 5.14 16.32 0.49
0.98 Yes 13 61.74 4.10 4.39 13.11 8.33 8.33 No 21 67.35 4.47 4.79
14.30 4.55 4.55 No 12 64.43 4.27 4.58 13.68 4.35 8.70 No 17 66.15
4.39 4.70 14.05 1.79 8.93 No 27 64.43 4.27 4.58 13.68 4.35 8.70 No
28 69.24 4.59 4.92 14.70 1.87 4.67 No 26 66.15 4.39 4.70 14.05 1.79
8.93 No 22 64.43 4.27 4.58 13.68 4.35 8.70 No 23 66.15 4.39 4.70
14.05 1.79 8.93 Yes 29 66.22 4.39 4.70 17.53 1.79 0.89 4.47 No 25
63.39 4.21 4.50 16.78 1.71 0.86 8.56 No 34 70.60 4.68 5.02 16.84
0.95 0.95 0.95 No 33 69.94 4.64 4.97 16.68 0.94 0.94 1.89 No 30
68.01 4.51 4.83 16.22 0.92 0.92 4.59 No 36 71.93 4.77 5.11 16.24
0.49 0.49 0.97 No
Since the product is designed to be a vapor permeable air barrier,
its vapor transmission was investigated as well. In addition, salt
leaching was investigated. Small molecules like sodium chloride can
leach out easily from the formed membrane, especially at high
dosage, e.g. formulations with 4.35-9.09% sodium chloride in the
composition (formulation nos. 11-13). When sodium chloride was used
at lower dosage (i.e., lower than 1% of total liquid composition
weight) combined with calcium nitrite (formulation nos. 25, 29, 30,
33, 34 and 36), there was no salt leaching out.
To investigate the drying time of the composition at -7.degree. C.
(20.degree. F.), non-freezing compositions were evaluated at
-7.degree. C. (20.degree. F.) for degree of drying vs. time. The
results were compared to the composition without freezing-point
lowering component (i.e. formulation no. 1) at normal temperature,
e.g. 21.degree. C. (70.degree. F.), and low temperature but above
freezing point, e.g. 4.degree. C. (40.degree. F.). All the tests
were carried at well controlled temperature and 50% RH. Each sample
was prepared in a 175 mm (3 in) plastic container at 2.3 mm (90
mil) wet thickness and the weight change was recorded over time.
The percent of drying completion was calculated by the equation
below.
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times..times..times..times..times..times. ##EQU00001## For
the low temperature compositions, the materials and testing
container were preconditioned at -7.degree. C. (20.degree. F.)
prior to testing. The results are graphically illustrated in FIG.
1.
The drying rate greatly depends on the property of additives and
amount of ethanol in the composition. Formulation nos. 31-34
achieve a similar degree of drying compared to the unaltered
regular composition (i.e. formulation no. 1) at 21.degree. C.
(70.degree. F.) and 4.degree. C. (40.degree. F.) in FIG. 1. The
formulations with high salt levels (e.g. formulation nos. 3 and 5
with more than 12% salt by total composition weight) dry slower,
probably because the salt may raise the boiling point and decrease
the volatility of the solvent (water). The composition with
propylene glycol could not dry for weeks at -7.degree. C.
(20.degree. F.) (not shown in FIG. 1).
Example 2
The effect of freezing-point lowering component, optionally with
evaporation enhancing component, on water vapor permeability and
elongation of membrane formed from the liquid coating composition
were tested and compared to the composition with no additives (i.e.
formulation no. 1). The liquid composition was applied by drawdown
bar at 2.2 mm (90 mil) wet thickness and tested per ASTM D412 for
elongation and ASTM D96 method B for water vapor permeability. All
the formulations (except formulation no. 1) were preconditioned
before application and cured at -7.degree. C. (20.degree. F.). The
unaltered composition (i.e. formulation no. 1) was preconditioned
and cured at 21.degree. C. (70.degree. F.) to provide a membrane
with vapor permeability of 15 perm and elongation of 419%. The
results of the test formulations compared to formulation no. 1 are
summarized in Table 2. It is noted that vapor permeability
increases with the addition of additives. Depending on the level
and properties of the additives, the tested compositions
demonstrate increases in permeability from 8 to 16.6 perm over that
of formulation no. 1. Elongation values are 61.4% to 355.5%,
respectively.
TABLE-US-00002 TABLE 2 Effect of low temperature additive on
permeability and elongation Composition Peremeability Formulation
Acrylic change comapred Elongation ID latex PVOH Filler Water
Ca(NO2)2 Nacl Ethanol to No 1 (perm) (%) 1 74.09 4.92 5.26 15.73
419.3 3 64.43 4.27 4.58 13.68 13.04 6 64.43 4.27 4.58 13.68 4.35
8.70 8.3 61.4 12 64.43 4.27 4.58 13.68 4.35 8.70 16.6 274.4 13
61.74 4.10 4.39 13.11 8.33 8.33 12.8 253.0 30 68.01 4.51 4.83 16.22
0.92 0.92 4.59 9.7 337.7 32 66.82 4.43 4.75 17.69 1.80 4.51 11.8
269.3 33 69.94 4.64 4.97 16.68 0.94 0.94 1.89 8.0 348.4 34 70.60
4.68 5.02 16.84 0.95 0.95 0.95 11.0 355.5
Example 3
Two tests were conducted to investigate the effectiveness of
various low temperature additives on corrosion resistance of a
metal surface in contact with the coating. One test is an
electrochemical test conducted on zinc-coated steel, which is a
typical metal used in construction. This test involves an
electrochemical impedance spectroscopy (EIS) measurement made in
0.5N sodium sulfate with 1N sulfuric acid to get pH 4 for ranking
membrane formed from different compositions.
The other test is an assembly of the liquid coating composition
coated onto Gypsum sheathing (e.g. DensGlass Gold from Georgia
Pacific) with zinc-coated steel attached to mimic actual materials
performance. The edge of metal was cut to expose the steel and the
whole assembly was placed in an environmental room at 21.degree. C.
(70.degree. F.) and 100% RH to accelerate the corrosion. The
assembly was taken out after two weeks and the zinc-coated steel
surface was inspected for corrosion compared to original
surface.
The results summarized in Table 3 indicate that zinc-coated steel
coated with the liquid coating composition containing only calcium
nitrite has the lowest conductance value, corresponding to the
lowest corrosion rate (conductance is the inverse of the
polarization resistance calculated from the electrochemical
impedance measurements). This result is in good agreement with the
acceleration study at 100% RH, where no visual corrosion was
observed. The composition with only sodium chloride exhibited
severe corrosion in the accelerated corrosion test. The composition
containing calcium nitrite and sodium chloride in a 2:1 ratio
exhibited greatly reduced corrosion on metal, similar to the
unaltered composition without salt, i.e. formulation no. 1. The
results indicate that calcium nitrite not only inhibits corrosion
by itself, but also retards the corrosion normally resulting from
sodium chloride.
TABLE-US-00003 TABLE 3 The effect of low temperature additive on
corrosion Composition Accelerated Acrylic polyvinyl Calcium Sodium
Sodium Propylene Conductance Corrosion (Two No latex alcohol Filler
Water nitrite chloride silicate CMA Ethanol Glycol- (Siemens) weeks
in RH 100%) 1 74.09 4.92 5.26 15.73 5.3E-03 Light 12 64.43 4.27
4.58 13.68 4.35 8.70 3.0E-03 Severe 17 66.15 4.39 4.70 14.05 1.79
8.93 3.3E-03 Severe 22 64.43 4.27 4.58 13.68 4.35 8.70 4.5E-03
Light 24 59.41 3.94 4.22 20.40 4.01 8.02 8.8E-04 Not observed 25
63.39 4.21 4.50 16.78 1.71 0.86 8.56 -- Light 27 64.43 4.27 4.58
13.68 4.35 8.70 3.5E-03 Light
Example 4
Various compositions were tested for freezing-point lowering,
drying at low temperature, VOC and flash point. The results are
summarized in Table 4 and FIG. 2. The results indicate that
equivalent drying rate and freezing point depression can be
achieved at low ethanol levels by utilizing a mixture of calcium
nitrite and sodium chloride in a 2:1 ratio (this ratio was selected
based on the corrosion study in Example 3). This composition also
has the additional benefit of very low VOC and high flash point,
which permits use without special equipment and personal protection
equipment.
TABLE-US-00004 TABLE 4 Formulations for VOC and Flash Point Study
Composition Flash Acrylic polyvinyl Calcium Sodium Freeze VOC Point
No latex alcohol Filler Water nitrite chloride Ethanol at 20 F.
(g/l) C. (F.) 32 66.82 4.43 4.75 17.69 1.80 4.51 No 113 42(108) 37
72.28 4.80 5.14 16.32 0.49 0.98 Yes 45 67.89 4.50 5.05 17.97 1.83
0.92 1.83 No 46 68.52 4.55 5.10 18.14 1.85 0.92 0.92 No 15 66(151)
47 70.10 4.65 5.22 16.72 0.95 0.47 1.89 No 48 70.77 4.69 5.27 16.88
0.95 0.48 0.96 Yes
Example 5
To provide flexibility to adjust to temperature changes in the
field, the feasibility of adding low temperature additives as a
single additive package into a regular, unaltered liquid coating
composition (i.e. formulation no 1 in Table 1, Part A) was
investigated. Base formulation no 32 was picked for investigation
purpose. Low temperature package (Part B) contains calcium nitrite
solution (35%)/ammonium hydroxide/ethanol at weight ratio of
52.83/2.25/44.92. For purpose of preparing this formulation,
calcium nitrite solution was obtained from Grace Construction
Products under the trade name DCI.RTM., while industrial grade
ethanol or denatured alcohol was obtained from Dow (SYNASOL.TM.
solvent 200 Proof PM-509). Ammonium hydroxide was used to adjust
the system pH above 8 and was obtained from National Ammonia. Part
B is mixed into Part A, which can be used at temperature above
4.degree. C. (40.degree. F.) alone, at a weight ratio of Part
A:Part B of 90:10 and stored at -7.degree. C. (20.degree. F.) prior
to spraying for property testing. As a comparison, Part A was
sprayed at normal environmental temperature around 23.degree. C.
(73.degree. F.) and tested. Both products were applied at 2.2 mm
(90 mil) wet thickness without sag observed. After 7 days cure, the
samples were tested per ASTM D412 for elongation, ASTM D96 method B
for water vapor permeability and ASTM E2178-03 for air permeance.
The samples sprayed on CMU were tested for 90 degree peel adhesion
at 50 mm/min. (2''/min) after 7 days cure.
The results, summarized in Table 5 below, indicate similar
performance except increased vapor transmission for the low
temperature formulation (Part A mixed with Part B), which results
from the salt additive.
TABLE-US-00005 TABLE 5 Part A mixed with Part B at 20 F. Part A at
73 F. Tensile strength (psi) 372.68 397.71 Elongation (%) 534.22
385.48 Vapor transmission (perm) 32.36 15.35 Peel adhesion on CMU
(pli) 35.93 Air permeance at 75 Pa (L/s/m2) 0.001 0.001
The preferred liquid coating composition of formulation no. 32,
shown in Tables 1, 2 and 4, may be applied below freezing
temperatures because it exhibits good freezing-point lowering and
acceptable drying time at low temperature. It also has acceptable
VOC and flash point for low temperature application and provides a
membrane having good flexibility and corrosion resistance. The low
temperature additives can be premixed into the formulation or the
additives can be packaged separately and mixed with the normal,
unaltered coating composition on-site for low temperature
application.
Other preferred formulations include formulation nos. 34 and 46,
which also provide good freezing-point lowering and acceptable
drying time at low temperature with minimized VOC, high flash point
and provides a membrane having good flexibility and corrosion
resistance.
* * * * *